91 - NAIL DISORDERS Flashcards
Complete or almost complete lack of the nail
anonychia, severe hypoplasia, or hyponychia
The condition is usually inborn, may be a genetic trait or the result of drug or toxin-induced lack of nail formation during embryogenesis. Several different types are known, ranging from a round tip of the digit without any visible change of the skin to an area that may correspond to the nail field, or a hyperkeratosis.
A condition when there is no terminal phalanx and no nail growth
Cooks syndrome or atelephalangia with anonychia
Hyponychia may be on all or several digits and is more common
Syndrome characerized by a particular form with half-side index fingernail hypoplasia and a Y-shaped radiologic alteration of the distal phalanx
Iso-Kikuchi syndrome
*image from google
may be a sign of phenytoin and alcohol fetopathy
Micronychia
This is also a constant feature of congenital onychodysplasia of Iso-Kikuchi (COIF [congenital onychodysplasia of index finger] syndrome).
short wide nail, mostly of the thumb, which develops from the age of 12 years on and is the result of a premature ossification of the epiphysis of the distal phalanx
Racket nail
The bone cannot grow longitudinally but continues to get broader because of apposition on the sides. This condition is autosomal dominant with variable expression and penetrance.
Very short nails may develop in patients under chronic hemodialysis who develop a tertiary hyperparathyroidism with resorption of the bone of the terminal phalanx.
brachyonychia
A rudimentary double nail of the fifth toe is a relatively frequent finding in subjects of all races. The nail may be slightly wider and have a slight longitudinal indentation or be discernable as a complete accessory nail (Fig. 91-1).1
Nail Discolorations (Chromonychia)
The nail may show a variety of color changes that may be caused by true coloration of the nail plate or alterations of the matrix and nail bed shining through the nail plate (Table 91-1).
most common color change
Leukonychia
What causes leukonychia?
It is caused by alterations in the keratinization of the nail plate with the nail cells being parakeratotic and/or having an eosinophilic cytoplasm in histologic sections. Often, these changes slowly disappear so that the free margin of the nail plate appears normal. Morphologically, there may be small patches or transverse bands, mainly seen in children and youngsters, probably the result of an overzealous manicure (Fig. 91-2). Total diffuse leukonychia (Fig. 91-3) is inborn in most cases. Subtotal diffuse leukonychia is sometimes seen in chronic liver disease. Many longitudinal white bands are characteristic for Hailey-Hailey disease.
result of nail bed pallor
Apparent leukonychia
It may disappear with temperature change or pressure. Muehrcke lines are a pair of 2 whitish transverse lines and are said to be a sign of hypalbuminemia (Fig. 91-4).
white surface of the nail, which is infected by fungi
Pseudoleukonychia
It was also termed (pseudo) leukonychia trichophytica although nondermatophyte molds also may be causative (Fig. 91-5).
term for red nails
Erythronychia
It may appear as red spots in the matrix (Fig. 91-6), 2 one or more longitudinal streaks in the distal matrix and nail bed (Figs. 91-7 and 91-8). Multiple red bands are commonly caused by inflammatory conditions such as lichen planus, whereas a single red band may represent specific tumors such as onychopapilloma (Fig. 91-7) or Bowen disease; hence a biopsy is indicated. Alternating narrow white and red bands are seen in Darier disease.
Erythronychia is the term for red nails. It may appear as red spots in the matrix (Fig. 91-6), 2 one or more longitudinal streaks in the distal matrix and nail bed (Figs. 91-7 and 91-8). Multiple red bands are commonly caused by inflammatory conditions such as lichen planus, whereas a single red band may represent specific tumors such as onychopapilloma (Fig. 91-7) or Bowen disease; hence a biopsy is indicated. Alternating narrow white and red bands are seen in Darier disease.
term for green nails
Chloronychia
In almost all cases, it is caused by a colonization of the nail by Pseudomonas aeruginosa. Often, 1 margin of the nail is involved with circumscribed swelling and detachment of the proximal nailfold, lack of the cuticle, and lateral onycholysis (Fig. 91-9). However, it is also seen in distal onycholysis and onycholysis over subungual tumors. Although Pseudomonas colonization is harmless for the patient, it may pose a risk for immunosuppressed individuals and these patients should not work in kitchens, bakeries, other food industry jobs, or in surgery, premature, and newborn wards and intensive care units.
treatment of choice of P. aeruginosa colonization
The treatment of choice of P. aeruginosa colonization is soaking in diluted white vinegar, 2 or 3 times daily for 10 minutes, then brushing the fingers dry. Household bleach for fingertip baths can be used undiluted or 1:1 diluted in water. Other disinfective agents may be used in addition. Topical antibiotics such as gentamycin are sometimes used, but are no more efficacious. Systemic antibiotics do not reach the site of infection because Pseudomonas mainly colonizes an onycholytic nail. In rare cases, systemic treatment with ciprofloxacin may be indicated.
Blue nails were seen developing in persons swimming in water with ________ as a disinfective agent.
copper sulfate
Slate-gray to bluish nail matrix is a sign of ________
argyria
denotes brown-to-black nail pigmentation
Melanonychia
Although this term is generally used for melanin pigmentation of the nail, many other agents may stain the nail brown, such as potassium permanganate or tobacco smoke.
Silver nitrate makes the nail jet-black (Fig. 91-10).
Some bacteria cause dirty grayish discoloration (Fig. 91-11).
Melanonychia may be diffuse and total, transverse or longitudinal. Usually, a brownto-black band develops in the nail running from the proximal nailfold into the free margin of the nail plate. It is caused by melanocyte activation, a lentigo, nevus, or melanoma of the matrix. Multiple melanonychias in several or all digits are common in dark-skinned individuals and Asians and are a physiologic phenomenon seen in almost all African Americans (Fig. 91-12). Pregnancy, a variety of drugs, vitamin B 12 deficiency, Addison disease, HIV infection, some dermatoses such as ungual lichen planus, and Bowen disease of the nail (particularly when associated with human papillomavirus [HPV] Type 56) may exhibit melanonychias. The association of lenticular labial, oral, and genital mucosal brown spots with melanonychias is characteristic for Laugier-Hunziker-Baran syndrome. Friction from rubbing shoes may cause longitudinal melanonychia of the little or big toenail, and onychophagia may cause melanocyte activation with subsequent melanonychia. Longitudinal nail pigmentation is the most frequent sign of nail melanoma and requires a meticulous evaluation. Single-digit melanonychia in an adult requires a biopsy.
A single, heavy trauma that is usually well-remembered because of its intense pain, or repeated microtraumas, most commonly from ill-fitting shoes or particular sports activities, lead to bleeding under the nail (Fig. 91-13).
SUBUNGUAL HEMATOMA
The blood is located between the overlying nail and the underlying matrix and nail bed epithelium and is therefore not degraded to hemosiderin by macrophages; consequently, it remains Prussian blue–negative or Perls stain–negative. With time it is included into the newly formed nail. It takes some months to slowly grow out but, in contrast to melanonychia, it never reaches into the free margin of the nail plate; this is one of the most reliable criteria for differential diagnosis. It also does not form a regular longitudinal band and when growing out a normal nail reappears. Dermatoscopy shows round red to dark-brown globules. Acute subungual hematoma can be drained by drilling a small hole into the nail plate to release the blood. Hematomas occupying more than 50% of the nail field are commonly associated with a fracture of the distal phalanx.
narrow red to almost black longitudinal lines in the distal nail bed and are caused by blood that is enclosed in the subungual keratin (Fig. 91-14).
Splinter hemorrhages
They develop either from thrombosed or ruptured capillaries that run longitudinally in the nail bed. They are characteristic for trauma, psoriasis, and some other inflammatory nail and systemic diseases, such as scleroderma, systemic lupus erythematosus, rheumatoid arthritis, antiphospholipid syndrome, and hematologic malignancies. Splinter hemorrhages also are characteristic for bacterial endocarditis with subsepsis lenta (39%) where they may occur together with Osler nodes (6.7%), Janeway lesions (2.2%), and retinal hemorrhages called Roth spots (3%). Oblique splinter hemorrhages may be a sign of trichinosis.
Detachment of the nail from the distal nail bed
onycholysis
All conditions with abnormal subungual hyperkeratosis will eventually cause onycholysis. These may be inflammatory nail diseases such as psoriasis (Fig. 91-15), lichen planus (Fig. 91-16), atopic dermatitis, and pityriasis rubra pilaris, or infections such as onychomycoses, or tumors of the nail bed.
What causes onycholysis semilunaris?
Direct trauma resulting from overzealous nail cleaning
This is characterized by sharply delimited proximal margins that may look like a half moon. Repeated frictional trauma is another cause, particularly in the asymmetric gait nail unit syndrome (see below).
Onycholysis is usually colonized by a variety of microorganisms, both bacteria and fungi. What is the treatment for onycholysis?
Treatment is the avoiding of moisture, cutting the nail back to the adherent part, brushing the nail bed twice daily with a disinfective solution, and applying an antimicrobial cream. Approximately one-half of the regrowing nail will remain attached to the nail bed; however, once having been onycholytic, a nail remains susceptible to reoccurrence of onycholysis.
Hyperkeratosis of the nail bed is a frequent event (Fig. 91-18). It is characteristic for onychomycoses where it contains most of the fungi, and for psoriasis. Other frequent causes are trauma, allergic and toxic contact, and atopic dermatitis. It is virtually always associated with onycholysis, except in pachyonychia congenita, where the nail covers an excessive nail bed hyperkeratosis in a horseshoelike fashion.
an exaggeration of nail bed and matrix hyperkeratosis
Onychogryposis (the common spelling, onychogryphosis, is etymologically incorrect as gryphos means a mythical animal that is half bird–half lion, whereas grypos means horn, hence it should be written onychogryposis)
It consists of innumerable stacks of keratin layers piled up one over the other, grows upward, is opaque and often has the shape of a ram’s horn. There is usually no contact with the nail bed anymore and the nail pocket is extremely short. It is mainly seen in elderly, neglected, and debilitated individuals (Fig. 91-19). Treatment is by nail avulsion, often completed by nail matrix cauterization to prevent regrowth of a grypotic nail.
bridging of the nail pocket by connective tissue, in most cases scars
Pterygium (from Greek for wing formation)
It is very common in lichen planus (Fig. 91-20), but is occasionally seen in other conditions, such as bullous pemphigoid, but particularly also after trauma. It first divides the nail into 2 parts, but may lead to complete nail destruction when it occupies almost the entire nail pocket.
When the nail plate does not separate correctly from the nail plate at the hyponychium and remains attached, a painful hyperkeratosis obliterates the distal groove. This is quite common in acral scleroderma and Raynaud syndrome, but also may be idiopathic (Fig. 91-21). Nail trimming can be very difficult and painful.
A temporary slowdown or even arrest of nail formation results in a transverse groove that runs parallel to the lunula border (Fig. 91-22).
It may be shallow at the lateral portions and deeper centrally.
result of a longer-lasting arrest of nail matrix proliferation that eventually results in a proximal gap in the nail and proximal onycholysis (Fig. 91-23).
Onychomadesis
It may end up in loss of the nail. The faster a nail grows the more pronounced the lesion; hence Beau lines and onychomadesis are much more common in fingernails than in toenails. Repeated Beau lines indicate repeated trauma, such as chemotherapy cycles. Equally distributed Beau lines hint at a general cause, whereas one-sided lines are seen after surgery of the extremity or a single-digit line at previous finger or toe surgery. A great many different causes are known, ranging from high fever to other serious diseases. Localized Beau lines and onychomadesis were also seen several weeks after hand-foot-and-mouth disease (coxcackievirus infection). Trauma, cosmetic manipulations, onychophagia, and onychotillomania are other causes and explain why the fingernails are predominantly affected (Table 91-2).
small depressions in the nail surface resulting from minute foci of abnormal keratinization in the apical matrix
Pits
This produces small mounds of parakeratosis that tend to break away from the nail when this emerges from under the proximal nailfold. Sometimes, the parakeratosis is not shed and small ivory-colored spots are seen. Pits are the most frequent sign of nail psoriasis (Fig. 91-24) where they are deep and of regular size, whereas those developing in alopecia areata and atopic dermatitis are more shallow and less-well delimited. Large surface defects are typical for pustular psoriasis and are called elkonyxis (Table 91-3).
term for rough nails (Fig. 91-25).
Trachyonychia
In addition to multiple pits, longitudinal striations and ridges such as seen in ungual lichen planus may cause this condition. When many nails are affected the diagnosis of 20-nail syndrome can be made.
result of pressure on the nail matrix, which is usually the result of a small tumor in the proximal nailfold (Fig. 91-26).
Longitudinal grooves
Causes of Beau lines and Onychomadesis
Causes of Pitting and Trachyonychia
hallmark of onychorrhexis
Brittle nails are a very common complaint in daily practice, particularly by women. Multiple longitudinal fissures, often associated with nail thinning and ridges, are the hallmark of onychorrhexis (Fig. 91-27). Defective keratinization is thought to be one of the causes.
lamellar splitting of the nail at its free end (Fig. 91-28).
Onychoschizia
It is usually confined to fingernails and occurs much more often in women than in men, pointing to the importance of environmental factors, such as frequent water contact that results in hydration and dehydration of the nail, which leaks cementing lipoproteins out. In babies with koilonychia of the big toenail, onychoschizia is common. Other causes are some dermatoses, onychomycosis, peripheral neuropathies and vascular disease, occupational traumas, and a variety of drugs, particularly those interfering with nail growth (Table 91-4). The role of nutrition is frequently overestimated.
Causes of Brittle Nails
most common type OF INGROWN NAIL
distal–lateral ingrowing of the edge of the big toenail (Fig. 91-29), rarely of neighboring toes, and even less frequently of fingers (Fig. 91-30)
How do ingrown nails develop?
There are many theories as to why and how ingrown nails develop and several are not exclusive of another one. Commonly, there is a discrepancy between too wide a nail plate and too narrow a nail bed. Usually, this is true for the distal portion where most pressure from shoes acts on the toes. The tip is compressed, it hurts, and the patient tries to cut the edge away, thereby leaving a kind of a spicule behind that pierces into the soft tissue of the distal portion of the nail sulcus causing pain, suppuration, granulation tissue, swelling, and, with time, fibrosis of the nailfold. 5 Further etiologic factors are tight socks, hyperhidrosis, and overcurvature of the nails.
Treatment of ingrown nails
Treatment is either conservative with insertion of a wisp of cotton between the offending nail and the nail sulcus, taping to pull the soft tissue away from the nail, or protection of the soft tissue from the nail margin by a gutter, which requires a local anesthesia. There are many more conservative approaches; however, all require consistent compliance from both the physician and the patient. Surgery is either to narrow the nail or to remove the swollen soft tissue (see Chap. 205).
Proximal ingrowing of the nail
retronychia
It is caused by a single strong or repeated minor trauma to the nail that eventually results in a backward movement of the nail plate. Most patients are children, adolescents, and young adults with 1 or 2 swollen, bluish, proximal nailfolds of their big toes (Fig. 91-31). The lunula is no longer present. On pressure, granulation tissue may emerge from under the nailfold. Careful clinical examination reveals that there is a major onycholysis of the nail that allows the plate to be pushed backward. This leads to a horizontal split in the matrix. As the nail bed is mainly responsible for the forward growth of the nail, this mechanism may no longer function and 1 or more new nails will be formed under the old proximal nail portion lifting this up. Its margin is very hard and sharp so that it cuts into the undersurface of the proximal nailfold with each step. The Y-shaped, W-shaped, or serrated proximal nail margin is well seen when the nail is avulsed, which is the treatment of choice.
Overcurvature of the nails
commonly called pincer nails, tubed nails, trumpet nails, and the like
The most common variant shows a distally increasing curvature (Fig. 91-32), but it may also remain at the same degree (tile nail) or exhibit sharp lateral bends. Half-side overcurvature is quite common.
2 types of pincer nails
- acquired - as a result of foot deformation, degenerative distal interphalangeal osteoarthritis (mainly in fingers), and some dermatoses, and
- hereditary - with symmetrical involvement of the big toenails and often some, but very rarely all, lesser toenails.
The big toenails show lateral deviation, the affected lesser nails are medially deviated. The base of the distal phalanx is widened, which can be felt by sliding palpation of the toe. Systematic radiographic examinations of the toes show that the distal phalanx is asymmetrical and often shows distally pointing exophytes that may correspond to the insertion of the interosseous ligament; they are much more pronounced medially than laterally, which explains in part the increasing lateral deviation of the nail plate. Furthermore, a distal dorsal traction osteophyte is commonly seen, which has to be removed when surgically flattening and spreading out the nail bed. In the distal portion, the overcurved nail pinches the nail bed and heaps it up, resulting in a reactive subungual hyperkeratosis.7 Treatment is by long-term application of nail braces to decrease the curvature, or a surgical procedure.
EFFECTS OF NAIL TREATMENT
The nails are not only subject to many environmental and traumatic influences, but also the target of cosmetic and medical treatments that often have a profound effect on the integrity of the nail. Nail hardeners are frequently prescribed for brittle nails. They contain formaldehyde that renders the nails harder and decreases their elasticity. Nail varnish is usually well tolerated but the tosyl formaldehyde resin may be the cause of allergic contact dermatitis. Artificial nails made from acrylics or cyanoacrylates may also cause contact dermatitis, often in the face and neck, less frequently of the nails; here, the reaction may persist for a long time, even after removal of the artificial nails, and be associated with long-lasting or even persisting pain. Gel nails are presently very popular. They are very hard and their removal requires harsh treatment with a coarse file that thins the nail plate and thus damages it. Chemical peels of the nail with 70% glycolic acid to improve their surface have been described8 ; their rationale remains to be clarified. Overzealous manicure is the cause of many untoward effects such as onycholysis semilunaris, wavy nail surface, loss of the cuticle with penetration of foreign substances under the proximal nailfold and subsequent paronychia, and bacterial colonization and infection. Urea in high concentrations is used to soften mycotic nails; urea 40% paste under occlusion for 3 to 5 days makes the infected nail portions soft enough to allow them to be scraped off.
the dermatosis with the most frequent nail involvement.
Psoriasis
At the time of consultation, approximately 50% of the patients present with nail changes. Over their lifetime, up to 90% of all psoriatics will develop nail alterations. The prevalence is even higher in psoriatic arthritis.
most frequent nail changes in psoriasis
pits, subungual hyperkeratosis, onycholysis, salmon spots, red lunulae, splinter hemorrhages, leukoplakia, and psoriatic paronychia.
ETIOLOGY AND PATHOGENESIS of nail psoriasis
There appears to be neither a gender nor race predilection. In contrast to skin, there is no association of human leukocyte antigen (HLA)-C0602 with nail and joint involvement, and nail psoriasis is often associated with inflammation at the insertion points of tendons and ligaments, giving rise to enthesitis. The nail lesions were thought to represent an aberrant response to tissue stressing of the integrated nail–joint apparatus, rather than being the result of an autoimmunity. The nail-and-joint disease may be linked to tissue-specific factors, including tissue biomechanical stressing and microtrauma that lead to activation of aberrant innate immune responses.9
most characteristic and most frequent signs of nail psoriasis
pits representing small, sharply delimited depressions in the nail surface of remarkably even size and depth
They may be haphazardly arranged or sometimes show parallel transverse or short longitudinal lines (Fig. 91-33). They are thought to arise from tiny psoriatic lesions in the apical matrix leading to parakeratosis that breaks off leaving these hole-like lesions.
When the parakeratosis remains it is seen as an ivory-colored spot in the proximal third of the nail plate (Fig. 91-34). Pits may be single, which is not yet psoriasis specific, or multiple. Ten pits per nail or more than 50 pits on all nails are seen as proof of nail psoriasis. Rarely, red spots are seen in the lunula usually representing a very active psoriasis lesion with dilation of the capillaries and thinning of the suprapapillary plate.
Complete nail destruction following crumbling of the plate is a sign of total matrix affection (Fig. 91-35).
seen when the psoriatic lesion is in the mid to distal matrix and parakeratotic cells are incorporated into the nail plate, making it optically appear white
Leukonychia
It is commonly an ill-defined white transverse band, but other morphologies are possible.
some millimeters long, reddish–dark-brown to black streaks of barely 1 mm in diameter.
They are analogous to the Auspitz phenomenon on the skin and result from damage to the dilated capillaries in the nail bed causing the blood to clot in these longitudinally arranged small vessels.
Splinter hemorrhages
They represent psoriatic plaques in the distal matrix and the nail bed.
The nail looks like paper on which a drop of oil has fallen: A yellowish-brownish spot with a red margin shines through the plate.
Salmon spots
The reason for this is that the squames of the psoriasis lesion are imbibed with serum and compressed under the nail. When such a salmon spot reaches the hyponychium, part of the parakeratosis breaks out and psoriatic onycholysis develops, which typically has a reddish proximal margin differentiating it from most other causes of onycholysis. In addition, there is often subungual hyperparakeratosis without oil-drop phenomenon causing onycholysis. Psoriatic hyperkeratosis may be marked and sometimes so extreme that it resembles pachyonychia congenita. Psoriasis involving both the dorsal and ventral surface of the proximal nailfold causes thickening and rounding of its free edge, which, in turn, are associated with loss of the cuticle, thus giving the pattern of chronic paronychia.
In psoriatic arthritis, nail involvement is often severe characterized by
psoriatic paronychia, complete nail destruction, and swelling of the distal interphalangeal joint.
a condition closely related to psoriatic arthritis but usually without obvious nail changes
Psoriatic pachydermoperiostosis
Mainly the big toe is considerably thickened and often painful.
3 different forms of pustular psoriasis
Pustular psoriasis occurs in 3 different forms, all of which also involve the nail.
In the palmar plantar pustular psoriasis of Barber-Königsbeck, all nail changes described above as well as larger surface defects called elkonyxis, plus subungual yellow spots representing large Munro abscesses may be seen (Fig. 91-36).
Generalized pustular psoriasis of von Zumbusch occasionally causes red areas with a rim of small pustules that may affect the nail. Subungual abscesses are frequent.
The most notorious form of pustular psoriasis is acrodermatitis continua suppurativa of Hallopeau. Often beginning with a single digit, the skin of the distal phalanx becomes red, develops some pustules that migrate under the nail and cause nail dystrophy, which, with time, may lead to complete disappearance of the nail unit so that only a red smooth digit tip is left until the disease slowly wanes off. However, acrodermatitis continua suppurativa may also initially involve several fingers and toes and run a very severe course (Fig. 91-37). A mutation in the gene for the interleukin-36 receptor antagonist leading to a defect in interleukin-36 receptor antagonist was found in generalized pustular psoriasis and acrodermatitis continua suppurativa, supporting the assumption that these conditions belong to the group of autoinflammatory diseases.
In the palmar plantar pustular psoriasis of Barber-Königsbeck, all nail changes described above as well as larger surface defects called elkonyxis, plus subungual yellow spots representing large Munro abscesses may be seen (Fig. 91-36).
The most notorious form of pustular psoriasis is acrodermatitis continua suppurativa of Hallopeau. Often beginning with a single digit, the skin of the distal phalanx becomes red, develops some pustules that migrate under the nail and cause nail dystrophy, which, with time, may lead to complete disappearance of the nail unit so that only a red smooth digit tip is left until the disease slowly wanes off. However, acrodermatitis continua suppurativa may also initially involve several fingers and toes and run a very severe course (Fig. 91-37).
systemic condition with characteristic joint, mucosal, eye, genitourinary, skin, and nail changes
Reiter disease, also known as reactive arthritis
The latter are very similar to pustular psoriasis although they usually have a more brownish tint because of the content of erythrocytes in the pustules (Fig. 91-38). Histopathology also shows spongiform pustules.
Differential Diagnosis of Nail Psoriasis and Onychomycosis
diagnosis of nail psoriasis
In most cases, nail psoriasis is diagnosed on clinical grounds. Skin lesions elsewhere plus 1 or several psoriatic nail features suggest the correct diagnosis. Histopathology is usually pathognomonic and helps to delineate nail psoriasis from other conditions, particularly onychomycosis. Reiter disease requires additional laboratory examinations.
Associations of psoriasis
Psoriasis is a frequent skin disease. Hence co-occurrence with other dermatoses that may also involve the nail is not exceptional. The most important association is that with onychomycosis as both conditions may look very similar, but a psoriatic nail may be colonized with pathogenic fungi and a true infection of the psoriatic nail is not infrequent (see Table 91-1).
COURSE of nail psoriasis
Why nail psoriasis often improves and worsens is unknown, although trauma may play an important role in the exacerbation of nail psoriasis. There may be periods without any nail alterations.
TREATMENT of nail psoriasis
Nail psoriasis is very resistant to almost all topical treatments whereas systemic therapies clearing the skin are usually also effective in nail psoriasis. The problem of all topical treatments is the penetration of the drug to the diseased tissue: through the nail plate in nail bed psoriasis, through all layers of the proximal nailfold plus the underlying nail in matrix lesions. Hence, pits, even though often being rather inconspicuous, are the most resistant to treatment. Nevertheless, a 3-month trial of a combination of a vitamin D 3 derivative with a potent corticosteroid is warranted. The less of the nail is present, the easier is penetration of the drug to the very psoriatic lesion. The list of other drugs tried is long and mostly comprises anecdotal reports and small case series. Injections of triamcinolone acetonide crystal suspension, 10 mg/mL every 6 weeks, into the proximal nailfold often improves nail psoriasis, but is painful and cumbersome for the patient. Methotrexate injections were also given with some success; however, this cytostatic drug may slow down nail growth and make an improvement visible only very late. The best treatment results are those with systemic antipsoriatic therapies, including biologics (see Chap. 28 for details).
In this context, the term ______ is used as a collective one comprising allergic contact dermatitis, toxic/ irritant contact dermatitis, atopic dermatitis, and nummular eczema; seborrheic eczema does not occur in the nail unit. They have a common denominator, the socalled spongiotic dermatitis.
eczema
Although differing in typical cases the clinical features may be similar between the different forms of eczema (Fig. 91-39), particularly in chronic eczema.
Clinical features of Acute allergic contact dermatitis of the nail
Acute allergic contact dermatitis exhibits redness of the periungual skin with tiny vesicles that tend to break and ooze. Serous crusts follow. Secondary infection with pyogenic micrococci leads to impetiginization. With time, oozing disappears, the redness decreases, and desquamation develops followed by cracking, particularly of the volar aspects and transition to the hyponychium and lateral nailfolds. The nails may become grossly deformed with deep asymmetric transverse furrows and ridges. Matrix and nail bed involvement is rather rare, but when present, for example, in patients with an allergy to artificial nails, may be painful. The nail itself loses its transparency as the spongiotic dermatitis of the matrix leads to inclusion of serum in the plate. The nail bed appears to be hyperkeratotic, even though this is a mixture of subungual keratin with serum inclusions. Chronic allergic contact dermatitis of the proximal nailfold leads to swelling, loss of the acute angle of its free margin with disappearance of the cuticle and separation of the underlying nail plate.
Clinical features of Toxic contact dermatitis of the nail
Toxic contact dermatitis rarely begins acute with erythema, vesicle formation, and oozing, such as from certain plants like garlic. Chronic irritant contact dermatitis is characterized by redness, scaling, fissures, and paronychia. It is often indistinguishable from chronic allergic dermatitis.
Two types of nail alterations in alopecia areata
- rough nails that have lost their shine and
- pitted nails with surface shine (Fig. 91-40).
Clinical features of Nail lichen planus
Nail lichen planus is a chronic disease that usually occurs in association with typical skin lesions (Figs. 91-41 and 91-42). Depending on the particular structure of the nail apparatus affected, variable clinical alterations develop. Most commonly, the apical matrix is involved leading to ridging, rough nails, loss of nail shine, longitudinal surface defects, and splits. Nail bed lichen planus is rare; it may cause subungual orthokeratosis with subsequent onycholysis. Even bullous lichen planus of the nails is possible. 20 Involvement of the proximal nailfold results in a bluish-red discoloration, sometimes associated with swelling. Longstanding nail lichen planus may lead to nail thinning and obliteration of the nail pocket with pterygium formation. The nail edge may look frayed. As the apical matrix is the site of the nail stem cells,21 scarring with permanent nail dystrophy may occur. Ulcerating nail lichen planus is very rare. Finally, a progressive nail atrophy may develop characterized by nail thinning and extreme fragility thus very similar to nails in amyloidosis.
Chronic paronychia with oozing and crust formation are the most common initial signs (Fig. 91-43), followed by onychomadesis (see Fig. 91-23) and sometimes by loss of the nail, of nail involvement.
Pterygium formation and permanent nail loss were observed in bullous pemphigoid, cicatricial pemphigoid, and acquired epidermolysis bullosa. Large clear periungual blisters are occasionally seen in bullous pemphigoid. They may be followed by erosions with crusting and sometimes superficial impetiginization. Pemphigus vegetans of the distal phalanx may resemble a very severe form of acrodermatitis continua suppurativa of Hallopeau with extensive pustulation and often a markedly pronounced pustular margin.
All these disorders may cause alterations of the nailfold capillaries. They may be reduced in number, dilated, tortuous, shorter, and show aneurysms and bleeding. This is easily seen when using a fluorescent dye that gives evidence of vessel leakage. However, even though often stressed in the rheumatologic literature, most of these changes do not allow a safe distinction to be made between them. Some changes are more typical for dermatomyositis, which is also characterized by Gottron papules of the dorsal aspect of phalanx, less frequently on the distal phalanx (Fig. 91-44). Periungual erythema and red lunula may be seen in acute lupus erythematosus whereas in chilblain lupus the changes reach from pernio-like nonspecific violaceous-blue hue with some telangiectasias to ulceration of the tip of the toe and the nail unit. Chronic discoid lupus erythematosus may cause red streaks in the nail bed, ridging of the nail, and dystrophy. White bands were seen in the diffusely brown nail of a black patient who had leukoderma of the head as a result of chronic discoid lupus erythematosus. Onycholysis, pterygium, and clubbing are nonspecific signs.24
Scleroderma with its acral variant often shows ulceration of the pulp and narrowing of the tip of the finger. The nail insidiously bends volarly giving the aspect of a parrot beak. The nail surface is dull and may show pronounced ridging. The plate is often nontransparent.
DIAGNOSIS of nail connective tissue disease
As isolated nail changes in these connective tissue diseases are exceptional, the diagnosis is usually made by their skin lesions and immunoserologically (Fig. 91-45). Capillary alterations are easily seen by dermatoscopy and laser scanning confocal microscopy; the latter also permits the blood flow to be observed.
Livedoid vasculopathy, also called livedo reticularis,
typical disorder of the legs that causes painful torpid ulcers
It is often called atrophie blanche when located in the ankle region. 25 It may affect the free margin of the proximal nailfold of toes, exhibiting lichenoid papules with reddening and white lines (Fig. 91-46).
The etiology and pathogenesis of the vasculitides and vasculopathies are not different from those of the skin lesions. Hypercoagulability in association with stasis are assumed to underlie livedoid vasculopathy. In infectious vasculitides, microbial thrombi are said to be responsible, but a general toxic response has also to be discussed.
Herpes Simplex of the Nail Apparatus - Clinical Features
The primary herpes simplex infection rarely causes nail lesions although virus inoculation may take place during the disease in fingersucking babies. Recurrent digital herpes simplex is occasionally seen in children, adolescents, and in certain professions, such as dentists (before they started routinely wearing gloves). Small vesicles are seen to develop that first have a clear content, which, after some days, becomes yellowish while the blisters tend to merge (Fig. 91-47). From the beginning, a visible red streak is commonly seen extending from the finger to the arm; this lymphangitis is usually associated with pain. After 7 to 10 days, the tenderness decreases, and the blister content may turn hemorrhagic and finally dry. After 2 to 3 weeks, the blister roof sheds.
Varicella and Herpes Zoster
Varicella may involve the nail region with a few characteristic vesicles, and herpes zoster may, although rarely, extend to the distal digits. The diagnosis is made from the skin lesions (Fig. 91-48). However, onychomadesis was observed in children several weeks after chickenpox; it may be assumed that unnoticed viral blisters of thematrix were the cause. Treatment follows the general rules of HHV3 therapy.
HPV clinical features
Common warts belong to the most frequent infections of humans. On the proximal nailfold, they are round papules with a rough keratotic surface; on the lateral folds they are often oval (Fig. 91-49). Subungual warts have an unspecific appearance often lifting the nail up and they are commonly painful. Under the proximal nailfold they raise it from the underlying nail and cause a marked swelling. At the hyponychium there may just be a rim-like thickening of the keratin that swells after 5 minutes in water.
Hand-foot-and-mouth disease is a vesicular disease characterized by intraoral aphthoid lesions that cause less discomfort than common aphthous ulcers, with small vesicles on the palms, soles, and around the nails (Fig. 91-50). They are usually oval in shape, the covering epidermis is gray from necrosis, and surrounded by a narrow erythematous rim. In ridged skin, the long axis of the vesicles is along the dermatoglyphics. Mild fever may be present in the beginning. Small outbreaks of this infection typically occur in spring and autumn. Many infections remain virtually asymptomatic and escape notice.
After approximately 6 weeks, some patients develop onychomadesis of single nails, probably as a sign of direct matrix involvement.26
The most characteristic bacterial infection is a bullous impetigo (Fig. 91-51) that runs around the proximal part of the nail, hence the common term runaround. It starts with a clear blister of the proximal and lateral nailfold that soon becomes putrid and often also hemorrhagic. Pain is usually mild. Extension under the nail is exceptional in adults, but may occur in children and is seen as a yellowish lake of pus under the nail. It is commonly painful.
Most of these infections are caused by staphylococci, rarely by streptococci. Subungual P. aeruginosa infections are rare. Small lacerations often from hangnails and other minor wounds are the portal of entry.
The course of the infections is sufficiently characteristic to make the correct diagnosis. Bacterial swabs may confirm the infection.
The main differential diagnosis is recurrent digital herpes simplex, which is more painful, develops a lymphangitis, and starts with a group of small clear blisters that coalesce and later becomes putrid.
P. aeruginosa is a ubiquitous pathogen quite frequently seen in the nail apparatus. Most cases are colonizations causing a green to brownish-black nail and often a localized marginal paronychia as evidenced by circumscribed swelling and loss of the cuticle (Fig. 91-52). Deep infections are rare in immunocompetent subjects.
The dorsal and ventral surfaces of the nails may be severely colonized by P. aeruginosa, which can form a bacterial biofilm.
The greenish color of the nail is very characteristic so that bacterial cultures are usually not needed to make the diagnosis. The color can be scraped off in most cases, but soon returns if the bacteria are not addressed.
Both exogenous and other enterobacteria causing a grayish discoloration, particularly Klebsiella spp. and Proteus spp., may have to be considered.
It appears that coinfection with yeasts and/or dermatophytes makes the nails more susceptible to Pseudomonas colonization.
Onychomycosis Facts
The nail apparatus is an extremely frequent site of infection for a great variety of different fungi. They may cause various acute, subacute and chronic infections. Fungal infections may be classified according to their pathogens into dermatophyte, yeast, and nondermatophyte mold infections, according to their time course (acute, subacute, subchronic, chronic), and, above all, according to their mechanism of infection (Table 91-6).
Onychomycoses affect toenails 7 to 10 times more frequently than they affect fingernails, which is thought to be attributable to the 3 times faster growth of fingernails as compared to toenails.
Onychomycoses are often seen as the most frequent nail disorders making up approximately 40% to 50% of all nail diseases. The vast majority are distal or distal–lateral subungual onychomycoses (Fig. 91-53). In the beginning, there is a distal subungual keratosis with an irregular border toward the nail bed. This slowly and insidiously progresses proximally while the nail may become discolored, nontransparent, and break distally. After some months or years, there is often no more progression but the subungual hyperkeratosis may continue to thicken. Often, there is a mild and inconspicuous desquamation around the nail or even an obvious tinea pedis is observed. Sometimes, a yellow streak develops that is formed like a narrow wedge in proximal direction. The lateral edge of the nail is frequently onycholytic.
Superficial white onychomycosis is a condition mostly seen on the toenails as chalky-white patches with no shine of the nail surface (Fig. 91-54). When occurring on fingernails, the white discoloration is inhomogeneous and more cloudy, but the nail surface remains shiny; this is the typical form of HIV infections (Fig. 91-55).
Proximal subungual onychomycosis is also rare. Clinically, it is seen as a white to yellowish discoloration of the nail that grows out from under the proximal nailfold (Fig. 91-56). The plate may be onycholytic under the whitish area. Repeated arched white lines are seen as recurrences from an internal focus.
All these different onychomycoses may lead to total dystrophic onychomycosis where the nail is substituted by irregular keratotic debris full of fungi. Primary total dystrophic onychomycosis is characteristic for chronic mucocutaneous candidiasis (Fig. 91-57), which represents a group of immune defects with impaired defense against Candida albicans. Chronic oral lesions, involvement of the scalp and other regions, and granulomatous lesions coexist.
Onychomycosis Treatments Approved by the U.S. Food and Drug Administration and Their Response Rates
characteristic sign of chronic hypoxemia and thus frequently indicates a cor pulmonale
Clubbing
The finger tips and often also the toe tips are enlarged, giving the look of a drumstick. The nail size is increased and both the longitudinal and transverse curvatures are more pronounced so that the nail is round like a watch glass (Fig. 91-58). Quite often, the lunula is very big. Nail bed and lunula are cyanotic. The angle between the proximal nailfold and the nail plate (angle of Lovibond) is greater than 180 degrees. When the 2 opposite fingers are held together, there is a narrow lozenge space between the proximal nail areas in normal persons whereas this diamond-shaped window is absent in clubbed nails, and the angle between the free nail margins is greater than 30 degrees (Schamroth sign).
Causes of Digit Clubbing
In addition, many other conditions are associated with clubbing (Table 91-8). Unilateral clubbing may hint at arterial insufficiency of this extremity. The cause of clubbing is still not known, but the prevailing hypothesis is that megakaryocytes are incompletely degraded to normal-size platelets in the lungs and may strand in the capillary network of the digits where they disintegrate and release their various growth factors.
Triad of Yellow Nail Syndrome (YNS)
- yellow, thick, extremely slow-growing nails with onycholysis, often also spontaneous nail loss and complete disappearance of the cuticle (Fig. 91-59),
- chronic sinus-bronchopulmonary infection and
- edema of the distal extremities
Chronic GI diseases and a variety of internal cancers also have been observed in association with the yellow nail syndrome.
Most nail changes seen in malnutrition, anorexia nervosa, bulimia, or kwashiorkor are nonspecific: the nails may be thin, brittle, and have lost their shine. In acrodermatitis enteropathica and acquired zinc deficiency there are often periungual erosions with crusting, the nail edges may break through the epidermis of the nail grooves and cause granulation tissue (Fig. 91-60). Very similar lesions are seen in glucagonoma dermatitis.
In severe liver disease, the nails may turn white and opaque. In Terry nails, a distal normal-colored band remains. Muehrcke lines are 2 parallel white bands in the middle of the nail bed that do not move out and are seen in severe hypoalbuminemia.
The nails may turn bluish in Wilson disease.
So-called half-and-half nails are seen in chronic renal insufficiency and under long-term hemodialysis. The proximal half of the nail is whitish, the distal half tends to be brownish (Fig. 91-61).
Systemic amyloidosis may have profound effects on the cutaneous appendages including the nails. They insidiously become thinner, fragile, ridged, and lose their shine, resembling late ungual lichen planus (Fig. 91-62). Subungual hemorrhage may occur.
A number of autoaggressive nail conditions are known that are commonly described as psychological disorders. Some are extremely frequent, such as chewing of the nails (onychophagia), picking of the periungual skin (perionychotillomania) and habitual pushing back of the cuticle and pressing on the lunula with another fingernail. Onychophagia is frequent in children, but it often lasts into adulthood (Fig. 91-63).
Perionychotillomania is more a condition of adults who continuously pull off hangnails and other tiny skin tags. This habit tic results in a central depression of the nail with a washboard aspect, an unusually long lunula and loss of the cuticle (Fig. 91-64).
This must not be confused with the Heller’s median canaliform dystrophy of the thumb nails, which is characterized by a median split in the nail plate that starts in the proximal portion, extends distally, and typically shows oblique furrows running proximally on both sides, thus giving the aspect of a Christmas tree (Fig. 91-65). Trauma is also the main cause.
More-severe autoaggressive behaviors are onychoteiromania where the nails are virtually rubbed away, onychotillomania where the nail is pulled out in pieces (Fig. 91-66), and onychotemnomania where a cutting device is used to remove all the nail. Onychodaknomania is a frankly psychotic behavior; the patients bite on their nails in the lunula or proximal nail bed region to produce pain. Many of these patients have a deprivation syndrome. 30 All these behavioral abnormalities are difficult to treat. Psychological support may be necessary. N-acetyl cysteine in a dose of 1800 to 2400 mg/day has been successfully used in a number of obsessive-compulsive disorders, including autoaggressive nail conditions. Nail chewing may spread periungual warts and lead to melanocyte activation with the development of brown streaks in the nails.
Drug-Induced Nail Alterations
Some drugs cause characteristic, although rarely specific, nail alterations (Table 91-9). They are most often observed under the treatment with cytostatic drugs. They may cause white lines, Beau lines, or onychomadesis, with the white lines being the least-severe and onychomadesis being the most-severe form of a similar reaction pattern, namely, growth retardation. Brown nail pigmentation may occur and represents an activation of matrix melanocytes. Taxanes cause painful subungual hemorrhagic abscesses that may require withdrawal of the drug. The use of frozen gloves and socks may partially prevent these adverse effects. Targeted anticancer therapies, particularly with epidermal growth factor receptor inhibitors and multiple kinase inhibitors, render the skin very fragile, leading the nail edge to break through and cause granulation tissue that looks similar to pyogenic granulomas.
This phenomenon is also seen under therapy with indinavir, a reverse transcriptase inhibitor, and retinoids. Retinoids are also associated with fragile nails and paronychia. Beta-blockers induce acral ischemia. Bleomycin may also lead to digital ischemia, and permanent nail loss was repeatedly seen after bleomycin treatment of periungual warts. Photochemotherapy with psoralens and ultraviolet A can induce multiple longitudinal brown streaks in several nails. Photoonycholysis is rarely seen during administration of some tetracyclines and fluoroquinolones, as it is painful, may be hemorrhagic, and occurs in the central nail bed of 1 or more nails. Its pathomechanism remains dubious as the nail plate absorbs almost all ultraviolet B and more than 95% of ultraviolet A light, and the skin is often not affected. Acyclovir does induce longitudinal melanonychias.
Pachyonychia congenita is a group of 5 molecular biologically well-defined diseases of cytokeratins KRT6a, KRT6b, KRT6c, KRT16, and KRT17. Its traditional classification into Type 1 Jadassohn-Lewandowsky syndrome and Type 2 Jackson-Lawler syndrome has now been abandoned as there were too many overlaps. Clinically, pachyonychia congenita shows painful callus-like palmar and plantar hyperkeratoses, monstrous thickening of the subungual hyperkeratosis that is covered by a horseshoe-like nail usually of normal thickness (Fig. 91-67), oral leukokeratosis with no potential for malignant degeneration, natal teeth, and vellus hair cysts. These cysts are mainly seen in KRT17 and KRT6a mutations. Nail changes occur in more than 80% of the patients and develop during infancy. Whether a late-onset pachyonychia congenita exists is not yet clear. Virtually all nails are affected. They are dark, appear thick (although this is the subungual keratosis), and the nail itself is overcurved and difficult to trim.
By definition, any hereditary disorder involving at least 2 of the cutaneous adnexa—hair, nails, sweat glands, and teeth—are ectodermal dysplasias. Roughly 30 of the more than 200 ectodermal dysplasias are now molecular biologically defined. For clinical convenience, the ectodermal dysplasias are subdivided into hidrotic and hypohidrotic ectodermal dysplasias. The most frequent ectodermal dysplasias are characterized by hair and nail involvement with normal sweat gland function and normal teeth, particularly the Clouston type, with dysplastic nails that often exhibit distally increasing plications, and are short, thickened, or brittle (Fig. 91-68). Three types of hypohidrotic ectodermal dysplasias are known, autosomal recessive, X-linked recessive, and autosomal dominant. Clinically, they present with hypoplastic nails, hypodontia, hypotrichosis, and inability to sweat adequately, which renders the babies at risk for hyperthermia when they are kept too warm. Frontal bossing and the characteristic midface hypoplasia give the affected individuals a very similar appearance, even when they belong to different races.
There are 3 distinct, large groups of hereditary bullous epidermolyses: simplex, junctional, and dystrophic. Nail lesions in the simplex types are rare, but are quite common in the course of the junctional and dystrophic bullous epidermolyses. Anonychia is the consequence of repeated blistering of the nail organ and leaves smooth digit tips covered with a shiny epidermis. One dystrophic epidermolysis bullosa is characterized by predominant nail lesions and hence called the nail type (Fig. 91-69). It may be identical with epidermolysis bullosa pruriginosa and pretibial epidermolysis bullosa. The big toenails are dystrophic and thickened; later the other toenails may follow. A pretibial reticular hyperkeratosis with tendency to develop blisters, and often itch, may be seen.
The group of ichthyoses is now called mendelian disorders of cornification. Nail changes are rare and not specific, such as rough nails and loss of surface shine.
Severe subungual hyperkeratoses similar to those of pachyonychia congenita were observed in a case of epidermolytic palmar plantar keratosis; however, the affected nail also exhibited a fungal infection, which might have triggered the hyperkeratosis (Fig. 91-70).
Congenital malalignment of the hallux nail, first described as congenital nail dystrophy, is a fairly common condition. The child may be born with normal nails and develop the condition later, or the nails may be abnormal at birth. Apparently, the disorder can also appear later in life, precipitated by a trauma in an individual with lateral deviation of the distal phalanx of the hallux. Sometimes only one side is affected. Identical twins may have identical unilateral involvement. In classical cases, the affected nail is triangular, thickened, oyster shell–like, discolored, and onycholytic. There is a false distal nailfold and a considerably shortened nail bed (Fig. 91-71). The degree of onycholysis and nail bed shrinkage determine the chances of spontaneous resolution and also of any type of treatment. If resolution has not started by the age of 2 years, it will likely not occur. Symptoms are rare and the children are often only presented to the dermatologist around puberty when the ugly nails are seen as an esthetic problem. Systematic radiographic examinations in more than 40 of our patients have shown that there is virtually always a lateral deviation of the distal phalanx called hallux valgus interphalangeus, a lateral deviation of the proximal great toe phalanx leading to classical hallux valgus, and a medial deviation of the first metatarsal bone because of an oblique distal surface of the first cuneiform bone. This forms an arch of the first ray, which self-perpetuates as a result of the action of the flexor and extensor hallux tendons. Early treatment by taping of this orthopedic abnormality is beneficial in those cases where the nail bed shrinkage, onycholysis, and distal nailfold are not too pronounced.
Onychocytic Matricoma
First described under the name subungual seborrheic keratosis, this name has now been abandoned in favor of onychocytic matricoma. 31 Clinically, there is a longitudinal brownish to dirty-yellow lesion under the nail that shines through the plate. Looking under the free margin of the nail reveals a thickening of keratotic material (Fig. 91-72). Surgical removal demonstrates an acanthoma histologically made up of mainly basaloid cells. Round keratin inclusions are similar to squamous eddies but their keratinization mode is via a keratogenous zone like normal nail formation.
Onychomatricoma
More than
200 cases of onychomatricoma have been reported since its first description in 1992. 32 It is a fibroepithelial neoplasm
originating from the matrix. The nail is thickened, funnel-shaped, yellow, striated, and may show splinter hemorrhages (Fig. 91-73). At the free end of the plate, small holes can be recognized. Dermatoscopy shows that the tunnels contain capillaries that may run a long distance distally in the nail; in rare cases they remain patent, and may cause bleeding upon nail trimming. This clinical appearance is caused by a densely cellular fibrous stroma with long filiform projections that are all covered with normal matrix epithelium extending into the nail. Thus the surface of nail-producing matrix is massively enlarged causing the nail thickening. Variants of this tumor are myxoid onychomatricoma and pigmented onychomatricoma, with pigmented onychomatricoma being an important differential diagnosis of subungual melanoma.
This is another recently described nail-specific tumor that arises from the distal matrix and produces a thread of abnormal keratin. Clinically, it is seen as a whitish, ivory-colored, yellowish, reddish, or light-brown band of 4 to 8 mm in width in the nail, similar to onychocytic matricoma (Fig. 91-74).
Onychopapilloma
End-on dermatoscopy of the nail shows, however, a circumscribed thinning of the nail plate over the keratotic distal end of the onychopapilloma. Often, the nail tends to break here and a V-shaped onycholysis develops in the distal nail bed. Treatment is by tangential excision of the entire lesion from the hyponychium to the mid-matrix.33
Fibrokeratomas of the nail unit are quite common. They are sausage-like lesions with a keratotic tip. Most arise from under the proximal nailfold and remain lying on it causing a longitudinal groove (Fig. 91-75). When a fibrokeratoma originates from the mid-matrix, it grows within the nail plate until the overlying nail lamella breaks away and a sharply delimited groove remains. Subungual fibrokeratomas arise from the most distal matrix or nail bed and cause a ridge. Multiple ungual fibrokeratomas, so-called Koenen tumors, are a sign of the tuberous sclerosis complex and occur in approximately 50% of these patients after the age of 12 years. Treatment is by incision around the tumor down to the bone and extirpation.
These lesions are very
common pseudotumors of middle-aged and elderly individuals and were known as “dorsal finger cysts.” Most occur in the proximal nailfold of the fingers, rarely on toes, where they exert pressure on the underlying matrix, resulting in a regular longitudinal groove (Fig. 91-76). When the lesion drains into the nail pocket the groove is very irregular, mirroring the periods of increased and released pressure. Subungual localization is rare and often seen as a violaceous lesion on one side of the matrix associated with hemi-overcurvature. Women are more frequently affected. Degenerative distal interphalangeal osteoarthritis with Heberden nodes is usually seen. Treatments vary from repeated punctures and expression of the viscous gelatinous mucin, to injection of steroids or sclerosants, infrared or laser coagulation, cryotherapy, and surgery. The recurrence rate is high except for the technique with intraarticular injection of methylene blue to visualize a potential connecting stalk to the joint, ligation of it, and meticulous extirpation of the myxoid material.
Although rare, this is the best- known nail tumor because of its highly characteristic symptoms. Patients usually present with the complaint of an extremely painful digit tip. Clinical examination reveals a violaceous red spot under the nail of a finger, from which a reddish line may sometimes extend distally (Fig. 91-77). The slightest shock and cold precipitate the pain that radiates into the arm. Probing allows to exactly locate the tumor, but variable high-frequency ultrasound and magnetic resonance tomography may sometimes be needed. Treatment is by meticulous enucleation of the tumor and repair of the matrix and nail bed.
Both lesions are often seen
as being the same condition and are confounded, although there are important differences. Osteochondromas arise from the epiphysis region of the distal phalanx and have a hyaline cartilage cap, whereas subungual exostoses originate from the corona unguicularis, are thus more distal, and have a fibrous cap. The nail plate is lifted up by a stone-hard nodule that, in case of exostosis, has a characteristic collarette-like margin representing the former border of the hyponychium (Fig. 91-78). Most subungual exostoses occur in children and young adults, commonly the big toe. Trauma was thought to be the cause. The recent finding of a chromosome translocation suggests a true tumor nature; however, it is not clear whether the examined lesions were exostoses or osteochondromas. A radiograph confirms the diagnosis and helps to preoperatively estimate the extent of surgery.
Squamous cell carcinoma is the most frequent malignant neoplasm of the nail. Its in situ form is Bowen disease. Most commonly seen around fingernails, Bowen disease may clinically resemble a flat agglomeration of warts (Fig. 91-79). Paronychia may be associated. Melanonychia is a feature in dark-skinned persons and association with HPV56. Other high-risk HPV are HPV16, HPV18, and HPV35, but many more were found, hinting at a possible genitodigital transmission. Bowen disease is slowly and insidiously growing and may result in large irregular periungual areas of velvety, red and scaling skin. Extension under the nail to the nail bed and matrix are common, and leukonychia is characteristic for matrix involvement. Ulceration and crust formation indicate invasive growth (Fig. 91-80), which is, however, a late event. Bone invasion and metastases are rare in the Bowen type of squamous cell carcinoma, but occur in the common squamous cell carcinoma type. Treatment of choice is Mohs surgery, but amputation is required in case of bone invasion.
Differential Diagnosis of Longitudinal Melanonychia
melanocyte activation in the matrix results in functional melanonychia. This is the rule for LM in pigmented persons, including many children (Fig. 91-81), because of repeated trauma, such as friction or onychophagia, during pregnancy, under chemotherapy, and a variety of other drugs.
A matrix lentigo is a numerical increase in melanin-producing cells (Fig. 91-82).
A matrix nevus is characterized by the nest-like agglomeration of melanocytes in the matrix; most are seen in children and are junctional (Fig. 91-83).
Pigmented melanoma of the matrix also causes LM (Fig. 91-84).
Periungual pigmentation is called the _________ and represents periungual spread of the in situ component (Fig. 91-85).
Hutchinson sign
Most subungual melanomas are pigmented and start with an LM, which is irregular in contrast to benign LMs (see Table 91-10).
Most subungual melanomas are pigmented and start with an LM, which is irregular in contrast to benign LMs (see Table 91-10). Proximal widening indicates rapid growth of the lesion. Nail dystrophy is a sign of an advanced melanoma. Dermatoscopy helps to determine the internal structure of the LM and allows a micro-Hutchinson sign to be seen. Approximately 25% to 33% of nail melanomas are amelanotic and pose great diagnostic challenges (Fig. 91-86). They usually arise from the nail bed, cause onycholysis that may ooze, and are frequently misdiagnosed as a pyogenic granuloma, ingrown nail, or wart, or even onychomycosis. Unfortunately, even pigmented nail melanomas are usually diagnosed very late with a diagnostic delay of years to decades. This is why the prognosis of nail melanomas is so poor, with 5-year survival rates of 15% to 20% for invasive nail melanomas.
Diagnostic Algorithm for Nail Melanomas—The ABCDEF Rule
A diagnostic algorithm considering several factors was proposed to facilitate the diagnosis of pigmented melanoma (Table 91-11); it is not useful for amelanotic melanomas and LM in children.
